DE1471955B2 - Process for the production of flat glass of different thicknesses - Google Patents

Description

30th

The invention relates to a method for producing flat glass of different thicknesses, in the case of the glass being fed into a bath of molten metal at a controlled rate to on the bath to form a layer of molten glass, and the layer in the form of a ribbon one regulated traction in the direction of movement along the bath is exposed and the simultaneous effect subject to surface tension and gravity and when moving along the Baths are cooled to the extent that it is sufficiently solidified to be undamaged at a controlled rate to be discharged from the bathroom.

In this known method (German patent specification 1 080 273) results from the free transverse flow of the glass and the tensile force exerted a flat glass of uniform thickness, which at the end of the Cross flow is achieved, the width of the glass ribbon being derived from the thickness of the glass ribbon and the fed Amount of glass results. It is provided there to reduce the thickness of the glass ribbon produced in this way, to increase the tensile force, while at the same time the previously achieved width of the glass ribbon by edge rolling is maintained. The previously achieved good surface properties can be impaired here will.

The invention is based on the object of developing the method mentioned at the beginning so that that flat glass with perfect surface properties in the desired thicknesses and widths can be produced while maintaining the throughput of the glass through the system.

This object is achieved in that the viscosity of the glass ribbon is ^{thermally reduced during its movement on the bath in the range of 10 3} to 10 ⁷ poise in such a way that, in cooperation with the regulated tensile force and unhindered transverse flow of the still flowable glass ribbon, the viscosity after a desired width and thickness of the glass ribbon is so large that further changes in shape of the glass ribbon are prevented.

As a result, the good surface properties resulting from the free transverse flow remain in full obtain.

The method according to the invention has the further advantage that the plant has a constant throughput can be operated and during operation by appropriate adjustment of the pulling force and the viscosity can be switched to a different thickness and thus width of the glass ribbon.

The constant throughput of the system results in the glass melting furnace for the glass to be fed in a uniform operation, which is useful to achieve the same quality of the glass. Through the possible quick changeover to other dimensions of the glass ribbon while the system is running will be theirs Utilization improved considerably.

In the drawing is an embodiment of an apparatus for the production of flat glass according to the Invention shown. In the drawing is

Fig. 1 is a sectional side view of a device for the production of flat glass in ribbon form according to the invention with a container for a bath. of molten metal, with means for feeding molten glass with regulated Speed to the bath and discharge devices for the glass ribbon of the desired shape,

F i g. Figure 2 is a top plan view of the inlet end of the bath tank of Figure 2. 1 and

F i g. 3 is a graph showing the relationship between the width and thickness of a glass ribbon shows, which is produced by the method according to the invention.

The plant has a continuously operated glass melting furnace with a forehearth 1 and a Control slide 2. Melted glass flows out of the glass melting furnace via the forehearth 1 to a drain, which consists of a lip 4 and side walls 5 ". The spout has a substantially rectangular one Cross-section.

The pouring lip 4 projects beyond an end wall 6 of a container for a bath 7 made of molten metal, which has the properties of the bath described in patent 1,010,247.

The bath is preferably made of molten tin or a tin alloy in which tin predominates. The one-piece container for the bath also has a bottom 8, side walls 9 and an end wall 10 at the outlet end of the bath. The mirror of the bath 7 made of molten metal is indicated at 11. Of the Container is designed so that the distance between its side walls 9 is greater than the width of the glass lying on the bath.

The bath tank is covered by a hood consisting of a roof 12, a vertically adjustable one End wall 13 at the inlet end of the bath, a roof part 14 above the spout 4, 5, side walls 15 and an end wall 16 at the outlet end of the bath. The hood encloses a tunnel-shaped one Room 17 above the bathroom.

The adjustable end wall 13 at the inlet end of the bath defines a narrow inlet 18 for molten material Glass 19, which flows from the pouring lip 4 onto the bath, around a layer 20 of molten Form glass on the bath.

3 4

The vertical distance of the pouring lip 4 to control the change in viscosity of the

the mirror 11 of the bathroom is several centimeters progressing glass band, the hood has a and is chosen so that a bead 21 of melted part 44, which has a bulge 45 of the nem glass is formed, which forms backwards under space 17. In this bulge are additional Spout 4, 5 up to the end wall 6 of the Badbehäl- 5 borrowed radiant heating devices 46 are arranged. At the ters extends. Container is a cooler 47 near the surface of the

The end walls 10 and 16 are arranged at the exit end of the glass ribbon, which schematically defines a narrow outlet 22 as a water bath. Outside the cooled box is shown. The cooler has one of the outlet discharge rollers 23 are arranged in such a way, flat heat-absorbing lower surface 40, on which their upper edge above the bottom of the outlet passes the glass ribbon as it moves,
let 22 lie. The solidified glass ribbon is controlled by the radiant heaters 46 and the cooler

The bath surface is lifted and freely adjustable by the outlet 47, this being separate or shared 22 promoted, can take place sampled from the discharge rollers 23 to the change in viscosity and is gripped by pairs of discharge rollers 25, 26. of the glass in the advancing glass ribbon.

The lower discharge rollers 23 and 25 are above 15 albeit the heating devices and the cooler Worm gear 27 with a main shaft 28 at a certain distance from the inlet of the bath bonds that have a continuously variable transmission, their effect extends up to 29 is coupled. An electric motor 30 drives the input into this area. Should the viscosity gradient in the output shaft 31 of the transmission 29. The rotational speed of the longitudinal direction is reduced, so is the main beam shaft 28 is increased by setting the transmission 20 ventilation heat from the heating devices 46. 29 adjusted by means of a handwheel 32. If, on the other hand, the viscosity gradient is to be increased,

The discharge lying above the glass ribbon is made effective by the cooler 47. Rolled under 26 are about worm gear 33 with a know operating conditions can be a fine control Upper shaft 34 connected, on which a sprocket of the viscosity gradient can be achieved when a 35 seated. This is via a chain 36 with a 25 simultaneous setting of the heating devices 46 Chain wheel 37 connected to the main shaft 28, so and the cooler 47 takes place.

that the interacting discharge rollers 25 and In the device shown, the falling

26 always fused glass 19 at the same controllable speed over the pouring lip 4 with a be driven to a controlled tensile force due to the vertical position of the control slide 2 the glass ribbon 24 to exercise. This tensile force determines a specific speed for the bath the speed of movement of the molten metal. The mobility of the glass 19 Glass along the bath of molten metal. the layer 20 of molten glass becomes at-Die Discharge rollers 23, 25 and 26 are in an inlet chamber, for example by means of radiant heating devices 49 of a conventional tunnel-shaped cooling furnace that regulates the space 17 near the front end wall 38 provided. Which are arranged on the solidified glass ribbon 24 35 13 of the hood. In modified The tensile force exerted by the discharge rollers can also control the side walls of the spout also the speed of movement of the heated.

molten glass along the bath before it flows. The molten glass 19 fed in pre-flows viscosity has reached at which the glass ribbon further downwards onto the surface of the bath of molten Changes in shape are no longer subject. 40 glass and forms a layer 20 of molten

The solidified ribbon of glass 24 carried by the bath outside glass, that carried along the bath under heat conditions has a sheen that is carried away by the fire that ensures that the polishing is melted equals a uniform thickness, zene glass unimpeded in the transverse direction to the limit flat surface and is free from damage to the flow of free river, thus creating a bath Surface. The ribbon of glass 24 passes through the cooling 45 floating body 50 of molten glass oven 38 in which it is tempered. After the outlet is formed, which has a uniform thickness, from the cooling furnace the glass ribbon is melted in a known manner from the floating body 50 of

Way cut into large slices, from which the zenem glass the solidified glass ribbon 24 is formed cut to standard sizes that are strong enough to fit its dimensions will. 5 ° to be maintained and undamaged from the bath through

In the roof 12 of the hood, the mechanical discharge rollers 23, 25 and 26 are provided with lines 39 connected to one another, which are gripped via branches, the tensile force on lines 40 being connected to feed lines 41 at the same time. the glass ribbon 24 is applied.
Through these lines, a protective gas is introduced into the order of the glass ribbon of the desired width

Room 17 initiated above the bath, which in 55 and thickness to give, the change is made to the essentials is completed. The protective gas is a viscosity of the glass in the advancing glass ribbon Gas that does not react chemically with the metal of the bath through thermal control, as previously described, so that impurities for the glass has not been ben. This regulation takes place in consultation can, as the exposed surfaces mung on the tensile force acting on the floating the bath and the part of the bath below the ab- 60 body 50 of molten glass is applied, raised part of the glass ribbon 24 from the protective This body is continuously gasified in thickness is covered. shrinks and reaches the desired thickness at the

The temperature of the bath in the bath tank becomes place where the viscosity of the glass is such that a regulated by temperature control devices 42, the further change in shape of the glass ribbon prevented are immersed in the bath. The room 17 above 65 is. That along the bath of molten metal The bath is heated by radiant heating, so the moving glass becomes both a controlled one is effected by heating means 43 which are subjected to tensile force in order to reduce its thickness, are arranged below the hood. as well as the effect of the forces from the surface

tension and gravity, which cause the formation of plane-parallel surfaces. The effect of the latter Forces is in turn dependent on the viscosity of the glass.

The thermal control of the changes in viscosity in the advancing glass ribbon by the heating devices 46 and / or the cooler 47 takes place in a viscosity range between 10 ³ to 10 ⁷ poise. At the upper limit of around 10 ⁷ poise, the glass has a viscosity that prevents further changes in shape. The actual viscosity of the glass at which any further substantial change in shape does not occur, however, depends on the tensile force which is exerted on the advancing glass by the solidified glass ribbon 24. For this reason, the setting of the heating devices 46 and the cooler 47 must be matched to the tensile force.

In order to refine the accuracy of controlling the final width and thickness of the glass ribbon 44, the change in viscosity change is controlled within the viscosity range of 10 ³ to 10 ⁷ poise, which results in small changes in the shape of the glass ribbon for trimming the glass ribbon.

The demands that the industry places on flat glass of different thicknesses for different purposes To be able to do justice, different manufacturing tolerances are required. It It is therefore desirable to find an expedient way of producing flat glass that different Widths and thicknesses of the ribbon of glass produced as it passes over the bath of molten Allowed to set metal. The shape changes of the advancing glass exist from a dilution by the action of the tensile force with simultaneous formation plane-parallel surfaces of the glass by the forces of surface tension and the Heaviness, where a change in width is associated with a change in thickness. The dependence between the width and thickness of the glass is subject to certain laws which are shown in FIG. 3 graphically are shown. In this illustration, the width of the glass ribbon is shown as ordinate 51, while the thickness of the glass ribbon is indicated as the abscissa 52. The families of curves shown correspond to different ones Viscosity gradients in the moving glass. The variable values along each curve are a Measure of the tensile force applied. The flatter the curve of the viscosity gradient, the more so The glass ribbon 24 can be made thinner, with a certain width given a required width Traction must be exerted.

If one works with a viscosity gradient, corresponding to curve 53 in FIG. 3, and one accordingly If the tensile force is set on the glass, a glass ribbon 6 mm thick and 2.5 m wide can be used can be achieved when the viscosity gradient and the tensile force match the value given by point 54 is equivalent to.

With the same throughput of glass, if a glass is thicker than 6 mm, but a Width of 2.5 m desired, by setting the cooler 47 with a steeper curve of the Viscosity gradient are worked, and the speed of the discharge rollers 23, 25 and 26 is reduced so that operating points, corresponding to point 55, result on curve 56. By using a flatter curve of the viscosity gradient with the aid of the heating devices 33 and an increase the speed of the discharge rollers 23, 25 and 26 results in an operating point 57 on the curve 58. A glass less than 6 mm thick and 2.5 m wide is then produced.

Through the coordinated control of the viscosity gradient in the glass within the range from 10 ³ to 10 ⁷ poise and the tensile force exerted, commercial glass of the desired width and thickness can therefore be produced.

In a modified way, instead of the cooling furnace connected behind the bath tank, the bath can be used as far be extended that the glass ribbon 24 at least partially before it is discharged from the Bad is remunerated.

Additional control of the width and thickness of the glass ribbon can be achieved by controlling the viscosity of the molten glass can be achieved if it is to form the layer 20 of molten glass is fed to the bathroom. For this scheme, too, families of curves, similar to the one in FIG. 3 shown, can be established showing the dependence between controlling the viscosity of the fed Glass and the already described control of the viscosity gradient in the progressive Express glass.

1 sheet of drawings

Claims (1)

Claim: A method of making flat glass of various thicknesses in which glass is fed to a bath of molten metal at a controlled rate to form a layer of molten glass on the bath, and the layer in the form of a ribbon is subjected to a controlled tensile force in the direction of travel along the bath and is subject to the simultaneous action of surface tension and gravity and is cooled as it moves along the bath so that it is sufficiently solidified to be able to be discharged from the bath undamaged at a controlled speed, characterized in that the viscosity of the glass ribbon is thermally reduced during its movement on the bath in the range of 10 ³ to 10 ⁷ poise in such a way that, in cooperation with the regulated tensile force and unhindered transverse flow of the still flowable glass ribbon, the viscosity after reaching a desired width and thickness of the glass ribbon is so great that far ere changes in shape of the glass ribbon are prevented.